I am writing from Toronto. I have created some vegetable beds already on my backyard lawn but I always removed the sod layer entirely before putting new soil and compost. Is it OK to cut the sod in flat sheets, including all roots, turn it upside down and leave it in place and later just cover with the new soil and compost? Will that kill the grass or will the grass grow again?
Thank you for contacting the Toronto Master Gardeners before digging up your sod and turning it over. You will be saving lots of time and physical work this year, because you do not actually have to dig up your lawn at all. In fact it will be better not to since your old lawn will decompose into wonderful nutritious soil for your vegetables. And with the City of Toronto pesticide ban in place, your lawn should be pesticide free.
The method we are recommending to create your vegetable garden is called lasagna gardening or sheet composting. You will be adding a layer of cardboard or newspapers followed by the addition of layers of organic matter that will rot down to your existing lawn over the winter, creating a vegetable plot ready for planting in the spring.
In the fall cover your lawn area with a layer of brown corrugated cardboard or three layers of newspapers. This layer should be made wet. Follow with alternating layers of brown matter (leaves, shredded newspapers, pine needles) and green matter (grass clippings, garden cuttings, fruit and vegetable scraps). Continue until the layers reach close to 2 feet and finish with compost, manure or top soil. Soil microbes, insects and worms will do the rest of the work for you over the winter and your garden plot will be ready to be planted in the spring.
All the best for your new vegetable garden!